Synthesis of peracetylated C-1-deoxyalditol- and C-glycoside-dipyrranes via dithioacetal derivatives

Abstract Dipyrranes bearing peracetylated mono- or disaccharidic C -1-deoxyalditol moieties were prepared from d -galactose, d -glucose, d -mannose, and lactose. A partially hydrolyzed polysaccharide (agarose) was also used as starting material for the synthesis of a disaccharide-containing C -glycoside dipyrrane. These compounds were synthesized as follows: the sugar starting materials were first submitted to a mercaptolysis–acetylation one-pot procedure (EtSH/HCl–Ac 2 O/pyridine). The resulting peracetylated diethyl dithioacetals were converted into dipyrranes through carbonyl deprotection (H 5 IO 6 , THF–Et 2 O) followed by TFA-catalyzed pyrrole condensation with yields up to 62%. Overall yields from sugar starting materials were up to 49%.